/Engine/Source/Runtime/CoreUObject/Public/UObject/PackedObjectRef.h
FPackedObjectRefrepresents a lightweight reference that can fit in the space of a pointer and be able to refer to an object (or null) that may or may not be loaded without pointing to its location in memory (even if it is currently loaded).
struct FPackedObjectRef
UPTRINT
EncodedRef
Must be 0 for a reference to null.